We recently located a rare cytokeratin-positive (CK+) type of microvascular endothelial cell (MVEC) in the corpus luteum and aorta. Bovine corpus luteum MVEC are known to be involved in the cyclic accumulation of eosinophils and macrophages. Since leukocyte migration is specifically mediated by adhesion molecules and the release of cytokines, we compared the expression of these factors in basal and TNF-α-stimulated CK+ MVEC and in common cytokeratin-negative (CK–) MVEC in order to obtain an initial insight into the functional capacities of CK+ MVEC. CK– MVEC revealed significantly higher basal RANTES mRNA expression than CK+ MVEC, and TNF- α up-regulated RANTES mRNA in both types of MVEC. Only resting and stimulated CK– MVEC expressed granulocyte-macrophage colony-stimulating factor mRNA. Both MVEC types expressed monocyte colony-stimulating factor mRNA, but remained negative for eotaxin and interleukin (IL)-5 mRNA even after stimulation. Resting CK+ MVEC were positive for CD29, CD31, CD49a and CD49e, but expressed most of these antigens at a significantly lower density than did CK– MVEC. In contrast to CK– MVEC, CK+ MVEC failed to express CD49b or MHC class II. The activation of CK+ MVEC with TNF-α induced the expression of CD62P, but not of CD49b or MHC class II. In summary, phenotypically variable MVEC derived from the microvascular bed of one organ differ in their TNF-α-regulated expression of cytokine mRNA and adhesion molecules. Morphological heterogeneity is related to a particular specialisation of functional MVEC.

OBJECTIVE: Leptin-deficient (ob/ob) mice are obese and infertile. Dysfunctions of the ovaries are preferentially related to leptin-deficiency. DESIGN: Morphological and molecular biological obesity-dependent changes in ob/ob ovaries. SUBJECTS: Ovaries were obtained from three-month-old mice either homozygote (ob/ob) and heterozygote (ob/ þ ) or wild-type (C57BL6, WT) for the investigation by light and electron microscopy, as well as for western blot analysis of lectin-like oxidised low density lipoprotein receptor (LOX-1), Toll-like receptor 4 (TLR4), CD36, cleaved caspase-3, microtubule-associated protein light chain 3 (LC3), and the steroidogenic acute regulatory protein (StAR). RESULTS: Compared with control ovaries with corpora lutea, ob/ob ovaries lacked corpora lutea, follicular atresia was at a higher rate; lipid droplets accumulated in follicle cells and in the oocyte with damaged mitochondria; the basement membrane of follicles was thickened. LOX-1 and CD36 expressions were comparable for all three groups. Ob/ob ovaries showed significantly higher levels of TLR4 and cleaved caspase-3 than the ones from the control groups. The high LC3-II/I ratio in the WT and ob/ þ ovaries was related to the presence of corpora lutea. The StAR protein was lower in the ob/ob ovaries signifying reduced steroidogenesis. CONCLUSIONS: Excessive lipid storage causes disorders of ovarian function in ob/ob mice. The local lipid overload leads to advanced follicular atresia with apoptosis and defect steroidogenesis. We suggest that the changes in lipid metabolism lead to increased oxidative stress and thereby, they are an important reason of anovulation and infertility.

Leucocytes vary in type and number during the lifespan of a corpus luteum. The aim of this study was to determine whether there is an increase in the number of lymphocytes and macrophages as a result of local proliferation. Bovine corpora lutea were classified into stages of development, secretion and regression. A new double immunolabelling method was established for nuclear Ki-67 antigen (a marker for cell proliferation) and for leucocyte surface antigens (detection of CD2-, CD3-, CD4-, CD8-positive lymphocytes and CD14-positive monocytes). Differential cell counting was performed. Between the stages of development and regression there was an increase in the number of T-lymphocytes and macrophages. The percentage of proliferating leucocytes in relation to the total number of proliferating cells was approximately 20% at the stage of advanced secretion and 70% at late regression. The increase in the number of proliferating leucocytes at late regression was due to CD14-positive macrophages. These macrophages migrated from small blood vessels into the septa of corpora lutea at the early stage of regression. Macrophages showed local proliferation in the late stage of regression when capillaries were no longer present. It is concluded that the physiological involution of the corpus luteum is an inflammatory-like condition, which includes local proliferation of monocytes.

The cyclic nature of the capillary bed in the corpus luteum offers a unique experimental model to examine the life cycle of endothelial cells, involving discrete physiologically regulated steps of angiogenesis, blood vessel maturation and blood vessel regression. The granulosa cells and theca cells of the developing antral follicle and the steroidogenic cells of the corpus luteum produce and respond to angiogenic factors and vasoactive peptides. Following ovulation the neovascularization during the early stages of corpus luteum development has been compared to the rapid angiogenesis observed during tumor formation. On the other end of the spectrum, the microvascular endothelial cells are the first cells to undergo apoptosis at the onset of corpus luteum regression. Important insights on the morphology and function of luteal endothelial cells have been gained from a combination of in vitro and in vivo studies on endothelial cells. Endothelial cells communicate with cells comprising the functional unit of the corpus luteum, i.e., other vascular cells, steroidogenic cells, and immune cells. This review is designed to provide an overview of the types of endothelial cells present in the corpus luteum and their involvement in corpus luteum development and regression. Available evidence indicates that microvascular endothelial cells of the corpus luteum are not alike, and may differ during the process of angiogenesis and angioregression. The contributions of vasoactive peptides generated by the luteal endothelin-1 and the renin-angiotensin systems are discussed in context with the function of endothelial cells during corpus luteum formation and regression. The ability of two cytokines, tumor necrosis factor alpha and interferon gamma, are evaluated as paracrine mediators of endothelial cell function during angioregression. Finally, chemokines are discussed as a vital endothelial cell secretory products that contribute to the recruitment of eosinophils and macrophages. The review highlights areas for future investigation of ovarian microvascular endothelial cells. The potential clinical applications of research directed on corpus luteum endothelial cells are intriguing considering reproductive processes in which vascular dysfunctions may play a role such as ovarian failure, polycystic ovary syndrome (PCOS), and ovarian hyperstimulation syndrome (OHSS).

Catalase/GPx activity in the supernatants may be due to cell death or to secretion. Oxidative stress could be sensed by CK(+) cells and indicated by changes in catalase/GPx activity in the follicular fluid during ovarian disorders.